/*
** $Id: lparser.c,v 2.42.1.3 2007/12/28 15:32:23 roberto Exp $
** Lua Parser
** See Copyright Notice in lua.h
*/


#include "luacore.h"

#include "lcode.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "llex.h"
#include "lmem.h"
#include "lobject.h"
#include "lopcodes.h"
#include "lparser.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"

#include "lparser.hxx"
#include "lcode.hxx"


#define hasmultret(k)		((k) == VCALL || (k) == VVARARG)

#define getlocvar(fs, i)	((fs)->f->locvars[(fs)->actvar[i]])

#define luaY_checklimit(fs,v,l,m)	if ((v)>(l)) errorlimit(fs,l,m)



/*
** prototypes for recursive non-terminal functions
*/
static void chunk (LexState *ls);
static void expr (LexState *ls, expdesc *v);


static void anchor_token (LexState *ls) {
  if (ls->t.token == TK_NAME || ls->t.token == TK_STRING) {
    TString *ts = ls->t.seminfo.ts;
    luaX_newstring(ls, getstr(ts), ts->len);
  }
}


static void error_expected (LexState *ls, int token) {
  luaX_syntaxerror(ls,
      luaO_pushfstring(ls->L, LUA_QS " expected", luaX_token2str(ls, token)));
}


static void errorlimit (FuncState *fs, int limit, const char *what) {
  const char *msg = (fs->f->linedefined == 0) ?
    luaO_pushfstring(fs->L, "main function has more than %d %s", limit, what) :
    luaO_pushfstring(fs->L, "function at line %d has more than %d %s",
                            fs->f->linedefined, limit, what);
  luaX_lexerror(fs->ls, msg, 0);
}


static int testnext (LexState *ls, int c) {
  if (ls->t.token == c) {
    luaX_next(ls);
    return 1;
  }
  else return 0;
}


static void check (LexState *ls, int c) {
  if (ls->t.token != c)
    error_expected(ls, c);
}

static void checknext (LexState *ls, int c) {
  check(ls, c);
  luaX_next(ls);
}


#define check_condition(ls,c,msg)	{ if (!(c)) luaX_syntaxerror(ls, msg); }



static void check_match (LexState *ls, int what, int who, int where) {
  if (!testnext(ls, what)) {
    if (where == ls->linenumber)
      error_expected(ls, what);
    else {
      luaX_syntaxerror(ls, luaO_pushfstring(ls->L,
             LUA_QS " expected (to close " LUA_QS " at line %d)",
              luaX_token2str(ls, what), luaX_token2str(ls, who), where));
    }
  }
}


static TString *str_checkname (LexState *ls) {
  TString *ts;
  check(ls, TK_NAME);
  ts = ls->t.seminfo.ts;
  luaX_next(ls);
  return ts;
}


static void init_exp (expdesc *e, expkind k, int i)
{
    e->f = e->t = NO_JUMP;
    e->k = k;
    e->u.s.info = i;
}

static void codestring (LexState *ls, expdesc *e, TString *s)
{
    FuncState *currentFuncState = GetCurrentFuncState( ls );

    init_exp(e, VK, luaK_stringK(currentFuncState, s));
}


static void checkname(LexState *ls, expdesc *e) {
  codestring(ls, e, str_checkname(ls));
}


static int registerlocalvar (LexState *ls, TString *varname)
{
    FuncState *fs = GetCurrentFuncState( ls );
    Proto *f = fs->f;
    size_t oldsize = f->sizelocvars;
    luaM_growvector(ls->L, f->locvars, fs->nlocvars, f->sizelocvars, SHRT_MAX, "too many local variables");
    while (oldsize < f->sizelocvars) f->locvars[oldsize++].varname = NULL;
    f->locvars[fs->nlocvars].varname = varname;
    luaC_objbarrier(ls->L, f, varname);
    return fs->nlocvars++;
}


#define new_localvarliteral(ls,v,n) \
  new_localvar(ls, luaX_newstring(ls, "" v, (sizeof(v)/sizeof(char))-1), n)

static void new_localvar (LexState *ls, TString *name, int n)
{
    FuncState *fs = GetCurrentFuncState( ls );
    luaY_checklimit(fs, fs->nactvar+n+1, LUAI_MAXVARS, "local variables");
    fs->actvar[fs->nactvar+n] = cast(unsigned short, registerlocalvar(ls, name));
}

static void adjustlocalvars (LexState *ls, int nvars)
{
    FuncState *fs = GetCurrentFuncState( ls );

    fs->nactvar = cast_byte(fs->nactvar + nvars);

    for (; nvars; nvars--)
    {
        getlocvar(fs, fs->nactvar - nvars).startpc = fs->pc;
    }
}

static void removevars (LexState *ls, int tolevel)
{
    FuncState *fs = GetCurrentFuncState( ls );

    while (fs->nactvar > tolevel)
    {
        getlocvar(fs, --fs->nactvar).endpc = fs->pc;
    }
}


static int indexupvalue (FuncState *fs, TString *name, expdesc *v) {
  int i;
  Proto *f = fs->f;
  size_t oldsize = f->sizeupvalues;
  for (i=0; i<f->nups; i++) {
    if (fs->upvalues[i].k == v->k && fs->upvalues[i].info == v->u.s.info) {
      lua_assert(f->upvalues[i] == name);
      return i;
    }
  }
  /* new one */
  luaY_checklimit(fs, f->nups + 1, LUAI_MAXUPVALUES, "upvalues");
  luaM_growvector(fs->L, f->upvalues, f->nups, f->sizeupvalues, MAX_INT, "");
  while (oldsize < f->sizeupvalues) f->upvalues[oldsize++] = NULL;
  f->upvalues[f->nups] = name;
  luaC_objbarrier(fs->L, f, name);
  lua_assert(v->k == VLOCAL || v->k == VUPVAL);
  fs->upvalues[f->nups].k = cast_byte(v->k);
  fs->upvalues[f->nups].info = cast_byte(v->u.s.info);
  return f->nups++;
}


static int searchvar (FuncState *fs, TString *n) {
  int i;
  for (i=fs->nactvar-1; i >= 0; i--) {
    if (n == getlocvar(fs, i).varname)
      return i;
  }
  return -1;  /* not found */
}


static void markupval (FuncState *fs, int level)
{
    BlockCnt *bl = (BlockCnt*)fs->blockList.GetFirst();

    while (bl && bl->nactvar > level)
    {
        bl = (BlockCnt*)bl->next;
    }

    if (bl) bl->upval = 1;
}


static int singlevaraux (FuncState *fs, TString *n, expdesc *var, int base)
{
    if (fs == NULL)
    {  /* no more levels? */
        init_exp(var, VGLOBAL, NO_REG);  /* default is global variable */
    }
    else
    {
        int v = searchvar(fs, n);  /* look up at current level */

        if (v >= 0)
        {
            init_exp(var, VLOCAL, v);

            if (!base)
            {
                markupval(fs, v);  /* local will be used as an upval */
            }
            return VLOCAL;
        }
        else
        {  /* not found at current level; try upper one */
            FuncState *upperState = (FuncState*)fs->next;

            if (singlevaraux(upperState, n, var, 0) != VGLOBAL)
            {
                var->u.s.info = indexupvalue(fs, n, var);  /* else was LOCAL or UPVAL */
                var->k = VUPVAL;  /* upvalue in this level */
                return VUPVAL;
            }
        }
    }

    return VGLOBAL;
}

static void singlevar (LexState *ls, expdesc *var)
{
    TString *varname = str_checkname(ls);
    FuncState *fs = GetCurrentFuncState( ls );

    if (singlevaraux(fs, varname, var, 1) == VGLOBAL)
    {
        var->u.s.info = luaK_stringK(fs, varname);  /* info points to global name */
    }
}

static void adjust_assign (LexState *ls, int nvars, int nexps, expdesc *e)
{
    FuncState *fs = GetCurrentFuncState( ls );
    int extra = nvars - nexps;

    if (hasmultret(e->k))
    {
        extra++;  /* includes call itself */

        if (extra < 0)
        {
            extra = 0;
        }

        luaK_setreturns(fs, e, extra);  /* last exp. provides the difference */

        if (extra > 1)
        {
            luaK_reserveregs(fs, extra-1);
        }
    }
    else
    {
        if (e->k != VVOID)
        {
            luaK_exp2nextreg(fs, e);  /* close last expression */
        }

        if (extra > 0)
        {
            int reg = fs->freereg;
            luaK_reserveregs(fs, extra);
            luaK_nil(fs, reg, extra);
        }
    }
}

static void enterblock (FuncState *fs, BlockCnt *bl, lu_byte isbreakable)
{
    bl->breaklist = NO_JUMP;
    bl->isbreakable = isbreakable;
    bl->nactvar = fs->nactvar;
    bl->upval = 0;
    fs->blockList.Insert( bl );
    lua_assert(fs->freereg == fs->nactvar);
}

static void leaveblock (FuncState *fs)
{
    BlockCnt *bl = (BlockCnt*)fs->blockList.GetFirst();

    // Remove the current block from visibility.
    fs->blockList.RemoveFirst();

    removevars(fs->ls, bl->nactvar);

    if ( bl->upval )
    {
        luaK_codeABC( fs, OP_CLOSE, bl->nactvar, 0, 0 );
    }

    /* a block either controls scope or breaks (never both) */
    lua_assert(!bl->isbreakable || !bl->upval);
    lua_assert(bl->nactvar == fs->nactvar);

    fs->freereg = fs->nactvar;  /* free registers */

    luaK_patchtohere(fs, bl->breaklist);
}


static void pushclosure (LexState *ls, FuncState *func, expdesc *v)
{
    FuncState *fs = GetCurrentFuncState( ls );
    Proto *f = fs->f;
    size_t oldsize = f->sizep;

    luaM_growvector(ls->L, f->p, fs->np, f->sizep, MAXARG_Bx, "constant table overflow");

    while ( oldsize < f->sizep )
    {
        f->p[ oldsize++ ] = NULL;
    }

    f->p[ fs->np++ ] = func->f;
    luaC_objbarrier( ls->L, f, func->f );

    init_exp( v, VRELOCABLE, luaK_codeABx(fs, OP_CLOSURE, 0, fs->np-1) );

    for ( int i = 0; i < func->f->nups; i++ )
    {
        OpCode o = (func->upvalues[i].k == VLOCAL) ? OP_MOVE : OP_GETUPVAL;

        luaK_codeABC(fs, o, 0, func->upvalues[i].info, 0);
    }
}


static void open_func (LexState *ls, FuncState *fs)
{
    lua_State *L = ls->L;
    Proto *f = luaF_newproto(L);

    // Add it to the list of function states.
    ls->fsList.Insert( fs );    /* linked list of funcstates */

    fs->f = f;
    fs->ls = ls;
    fs->L = L;
    fs->pc = 0;
    fs->lasttarget = -1;
    fs->jpc = NO_JUMP;
    fs->freereg = 0;
    fs->nk = 0;
    fs->np = 0;
    fs->nlocvars = 0;
    fs->nactvar = 0;
    fs->blockList.Clear();
    f->source = ls->source;
    f->maxstacksize = 2;  /* registers 0/1 are always valid */
    fs->h = luaH_new(L, 0, 0);

    // Proto and table are not being collected, as they have a ref from being constructed.
}


static void close_func (LexState *ls)
{
    lua_State *L = ls->L;
    FuncState *fs = (FuncState*)ls->fsList.GetFirst();
    Proto *f = fs->f;

    removevars(ls, 0);
    luaK_ret(fs, 0, 0);  /* final return */
    luaM_reallocvector(L, f->code, f->sizecode, fs->pc);
    f->sizecode = fs->pc;
    luaM_reallocvector(L, f->lineinfo, f->sizelineinfo, fs->pc);
    f->sizelineinfo = fs->pc;
    luaM_reallocvector(L, f->k, f->sizek, fs->nk);
    f->sizek = fs->nk;
    luaM_reallocvector(L, f->p, f->sizep, fs->np);
    f->sizep = fs->np;
    luaM_reallocvector(L, f->locvars, f->sizelocvars, fs->nlocvars);
    f->sizelocvars = fs->nlocvars;
    luaM_reallocvector(L, f->upvalues, f->sizeupvalues, f->nups);
    f->sizeupvalues = f->nups;
    lua_assert(luaG_checkcode(f) == true);
    lua_assert(fs->blockList.IsEmpty() == true);
    
    // Remove this function state from existence.
    ls->fsList.RemoveFirst();

    // Dereference the table again.
    // We keep the reference on the proto, because it is the result object.
    fs->h->DereferenceGC( L );

    /* last token read was anchored in defunct function; must reanchor it */
    if ( fs )
    {
        anchor_token(ls);
    }
}


Proto *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff, const char *name)
{
    struct LexState lexstate;
    struct FuncState funcstate;
    lexstate.buff = buff;

    TString *inputNameString = luaS_new(L, name);

    try
    {
        luaX_setinput(L, &lexstate, z, inputNameString );

        open_func(&lexstate, &funcstate);
        try
        {
            funcstate.f->is_vararg = VARARG_ISVARARG;  /* main func. is always vararg */

            luaX_next(&lexstate);  /* read first token */

            chunk(&lexstate);
            check(&lexstate, TK_EOS);
        }
        catch( ... )
        {
            close_func(&lexstate);

            // We do not need the proto anymore.
            funcstate.f->DereferenceGC( L );
            throw;
        }
        close_func(&lexstate);

        // The result is funcstate.f, which is a referenced proto.
    }
    catch( ... )
    {
        // When done parsing, we should clear up the string.
        inputNameString->DereferenceGC( L );
        throw;
    }

    inputNameString->DereferenceGC( L );

    lua_assert(funcstate.next == NULL);
    lua_assert(funcstate.f->nups == 0);
    lua_assert(lexstate.fsList.IsEmpty() == true);
    return funcstate.f;
}



/*============================================================*/
/* GRAMMAR RULES */
/*============================================================*/


static void field (LexState *ls, expdesc *v)
{
    /* field -> ['.' | ':'] NAME */
    FuncState *fs = GetCurrentFuncState( ls );
    expdesc key;
    luaK_exp2anyreg(fs, v);
    luaX_next(ls);  /* skip the dot or colon */
    checkname(ls, &key);
    luaK_indexed(fs, v, &key);
}


static void yindex (LexState *ls, expdesc *v)
{
    /* index -> '[' expr ']' */
    luaX_next(ls);  /* skip the '[' */
    expr(ls, v);
    luaK_exp2val(GetCurrentFuncState( ls ), v);
    checknext(ls, ']');
}


/*
** {======================================================================
** Rules for Constructors
** =======================================================================
*/


struct ConsControl
{
    expdesc v;  /* last list item read */
    expdesc *t;  /* table descriptor */
    int nh;  /* total number of `record' elements */
    int na;  /* total number of array elements */
    int tostore;  /* number of array elements pending to be stored */
};

static void recfield (LexState *ls, struct ConsControl *cc)
{
    /* recfield -> (NAME | `['exp1`]') = exp1 */
    FuncState *fs = GetCurrentFuncState( ls );
    int reg = fs->freereg;
    expdesc key, val;

    if (ls->t.token == TK_NAME)
    {
        luaY_checklimit(fs, cc->nh, MAX_INT, "items in a constructor");
        checkname(ls, &key);
    }
    else  /* ls->t.token == '[' */
    {
        yindex(ls, &key);
    }

    cc->nh++;

    checknext(ls, '=');
    int rkkey = luaK_exp2RK(fs, &key);
    expr(ls, &val);

    luaK_codeABC(fs, OP_SETTABLE, cc->t->u.s.info, rkkey, luaK_exp2RK(fs, &val));
    fs->freereg = reg;  /* free registers */
}

static void closelistfield (FuncState *fs, struct ConsControl *cc)
{
    if (cc->v.k == VVOID)
    {
        return;  /* there is no list item */
    }

    luaK_exp2nextreg(fs, &cc->v);
    cc->v.k = VVOID;

    if (cc->tostore == LFIELDS_PER_FLUSH)
    {
        luaK_setlist(fs, cc->t->u.s.info, cc->na, cc->tostore);  /* flush */
        cc->tostore = 0;  /* no more items pending */
    }
}

static void lastlistfield (FuncState *fs, struct ConsControl *cc)
{
    if (cc->tostore == 0)
    {
        return;
    }

    if (hasmultret(cc->v.k))
    {
        luaK_setmultret(fs, &cc->v);
        luaK_setlist(fs, cc->t->u.s.info, cc->na, LUA_MULTRET);

        cc->na--;  /* do not count last expression (unknown number of elements) */
    }
    else
    {
        if (cc->v.k != VVOID)
        {
            luaK_exp2nextreg(fs, &cc->v);
        }

        luaK_setlist(fs, cc->t->u.s.info, cc->na, cc->tostore);
    }
}

static void listfield (LexState *ls, struct ConsControl *cc)
{
    expr(ls, &cc->v);
    luaY_checklimit(GetCurrentFuncState( ls ), cc->na, MAX_INT, "items in a constructor");

    cc->na++;
    cc->tostore++;
}

static void constructor (LexState *ls, expdesc *t)
{
    /* constructor -> ?? */
    FuncState *fs = GetCurrentFuncState( ls );
    int line = ls->linenumber;
    int pc = luaK_codeABC(fs, OP_NEWTABLE, 0, 0, 0);

    struct ConsControl cc;
    cc.na = cc.nh = cc.tostore = 0;
    cc.t = t;

    init_exp(t, VRELOCABLE, pc);
    init_exp(&cc.v, VVOID, 0);  /* no value (yet) */
    luaK_exp2nextreg(fs, t);  /* fix it at stack top (for gc) */
    checknext(ls, '{');

    do
    {
        lua_assert(cc.v.k == VVOID || cc.tostore > 0);

        if (ls->t.token == '}')
        {
            break;
        }

        closelistfield(fs, &cc);

        switch(ls->t.token)
        {
        case TK_NAME:
        {  /* may be listfields or recfields */
            luaX_lookahead(ls);
            if (ls->lookahead.token != '=')  /* expression? */
            {
                listfield(ls, &cc);
            }
            else
            {
                recfield(ls, &cc);
            }
            break;
        }
        case '[':
        {  /* constructor_item -> recfield */
            recfield(ls, &cc);
            break;
        }
        default:
        {  /* constructor_part -> listfield */
            listfield(ls, &cc);
            break;
        }
        }
    }
    while (testnext(ls, ',') || testnext(ls, ';'));

    check_match(ls, '}', '{', line);
    lastlistfield(fs, &cc);

    SETARG_B(fs->f->code[pc], luaO_int2fb(cc.na)); /* set initial array size */
    SETARG_C(fs->f->code[pc], luaO_int2fb(cc.nh));  /* set initial table size */
}

/* }====================================================================== */

static void parlist (LexState *ls)
{
    /* parlist -> [ param { `,' param } ] */
    FuncState *fs = GetCurrentFuncState( ls );
    Proto *f = fs->f;
    int nparams = 0;

    f->is_vararg = 0;

    if (ls->t.token != ')')
    {  /* is `parlist' not empty? */
        do
        {
            switch (ls->t.token)
            {
            case TK_NAME:
            {  /* param -> NAME */
                new_localvar(ls, str_checkname(ls), nparams++);
                break;
            }
            case TK_DOTS:
            {  /* param -> `...' */
                luaX_next(ls);
                f->is_vararg |= VARARG_ISVARARG;
                break;
            }
            default:
            {
                luaX_syntaxerror(ls, "<name> or " LUA_QL("...") " expected");
                break;
            }
            }
        }
        while (!f->is_vararg && testnext(ls, ','));
    }
    adjustlocalvars(ls, nparams);

    f->numparams = cast_byte( fs->nactvar - (f->is_vararg & VARARG_HASARG) );

    luaK_reserveregs(fs, fs->nactvar);  /* reserve register for parameters */
}

static void body (LexState *ls, expdesc *e, int needself, int line)
{
    /* body ->  `(' parlist `)' chunk END */
    FuncState new_fs;
    open_func(ls, &new_fs);
    try
    {
        new_fs.f->linedefined = line;
        checknext(ls, '(');
        if (needself)
        {
            new_localvarliteral(ls, "self", 0);
            adjustlocalvars(ls, 1);
        }
        parlist(ls);
        checknext(ls, ')');
        chunk(ls);
        new_fs.f->lastlinedefined = ls->linenumber;
        check_match(ls, TK_END, TK_FUNCTION, line);
    }
    catch( ... )
    {
        close_func(ls);

        // We do not need the proto anymore.
        new_fs.f->DereferenceGC( ls->L );
        throw;
    }
    close_func(ls);
    pushclosure(ls, &new_fs, e);

    // Terminate the FuncState again.
    new_fs.f->DereferenceGC( ls->L );
}

static int explist1 (LexState *ls, expdesc *v)
{
    /* explist1 -> expr { `,' expr } */
    int n = 1;  /* at least one expression */

    expr(ls, v);

    FuncState *fs = GetCurrentFuncState( ls );

    while (testnext(ls, ','))
    {
        luaK_exp2nextreg(fs, v);
        expr(ls, v);
        n++;
    }
    return n;
}

static void funcargs (LexState *ls, expdesc *f)
{
    FuncState *fs = GetCurrentFuncState( ls );
    expdesc args;
    int base, nparams;
    int line = ls->linenumber;

    switch (ls->t.token)
    {
    case '(':
    {  /* funcargs -> `(' [ explist1 ] `)' */
        if (line != ls->lastline)
        {
            luaX_syntaxerror(ls,"ambiguous syntax (function call x new statement)");
        }

        luaX_next(ls);

        if (ls->t.token == ')')  /* arg list is empty? */
        {
            args.k = VVOID;
        }
        else
        {
            explist1(ls, &args);
            luaK_setmultret(fs, &args);
        }

        check_match(ls, ')', '(', line);
        break;
    }
    case '{':
    {  /* funcargs -> constructor */
        constructor(ls, &args);
        break;
    }
    case TK_STRING:
    {  /* funcargs -> STRING */
        codestring(ls, &args, ls->t.seminfo.ts);
        luaX_next(ls);  /* must use `seminfo' before `next' */
        break;
    }
    default:
    {
        luaX_syntaxerror(ls, "function arguments expected");
        return;
    }
    }

    lua_assert(f->k == VNONRELOC);

    base = f->u.s.info;  /* base register for call */

    if (hasmultret(args.k))
    {
        nparams = LUA_MULTRET;  /* open call */
    }
    else
    {
        if (args.k != VVOID)
        {
            luaK_exp2nextreg(fs, &args);  /* close last argument */
        }

        nparams = fs->freereg - (base+1);
    }

    init_exp(f, VCALL, luaK_codeABC(fs, OP_CALL, base, nparams+1, 2));

    luaK_fixline(fs, line);

    fs->freereg = base+1;  /* call remove function and arguments and leaves (unless changed) one result */
}

/*
** {======================================================================
** Expression parsing
** =======================================================================
*/

static void prefixexp (LexState *ls, expdesc *v)
{
    /* prefixexp -> NAME | '(' expr ')' */
    switch (ls->t.token)
    {
    case '(':
    {
        FuncState *fs = GetCurrentFuncState( ls );

        int line = ls->linenumber;
        luaX_next(ls);
        expr(ls, v);
        check_match(ls, ')', '(', line);
        luaK_dischargevars(fs, v);
        break;
    }
    case TK_NAME:
    {
        singlevar(ls, v);
        break;
    }
    default:
    {
        luaX_syntaxerror(ls, "unexpected symbol");
        break;
    }
    }
}

static void primaryexp (LexState *ls, expdesc *v)
{
    /* primaryexp -> prefixexp { `.' NAME | `[' exp `]' | `:' NAME funcargs | funcargs } */
    FuncState *fs = GetCurrentFuncState( ls );
    prefixexp(ls, v);

    for (;;)
    {
        switch (ls->t.token)
        {
        case '.':
        {  /* field */
            field(ls, v);
            break;
        }
        case '[':
        {  /* `[' exp1 `]' */
            expdesc key;
            luaK_exp2anyreg(fs, v);
            yindex(ls, &key);
            luaK_indexed(fs, v, &key);
            break;
        }
        case ':':
        {  /* `:' NAME funcargs */
            expdesc key;
            luaX_next(ls);
            checkname(ls, &key);
            luaK_self(fs, v, &key);
            funcargs(ls, v);
            break;
        }
        case '(':
        case TK_STRING:
        case '{':
        {  /* funcargs */
            luaK_exp2nextreg(fs, v);
            funcargs(ls, v);
            break;
        }
        default:
            return;
        }
    }
}

static void simpleexp (LexState *ls, expdesc *v)
{
    /* simpleexp -> NUMBER | STRING | NIL | true | false | ... | constructor | FUNCTION body | primaryexp */
    switch (ls->t.token)
    {
    case TK_NUMBER:
    {
        init_exp(v, VKNUM, 0);
        v->u.nval = ls->t.seminfo.r;
        break;
    }
    case TK_STRING:
    {
        codestring(ls, v, ls->t.seminfo.ts);
        break;
    }
    case TK_NIL:
    {
        init_exp(v, VNIL, 0);
        break;
    }
    case TK_TRUE:
    {
        init_exp(v, VTRUE, 0);
        break;
    }
    case TK_FALSE:
    {
        init_exp(v, VFALSE, 0);
        break;
    }
    case TK_DOTS:
    {  /* vararg */
        FuncState *fs = GetCurrentFuncState( ls );

        check_condition(ls, fs->f->is_vararg, "cannot use " LUA_QL("...") " outside a vararg function");

        fs->f->is_vararg &= ~VARARG_NEEDSARG;  /* don't need 'arg' */
        init_exp(v, VVARARG, luaK_codeABC(fs, OP_VARARG, 0, 1, 0));
        break;
    }
    case '{':
    {  /* constructor */
        constructor(ls, v);
        return;
    }
    case TK_FUNCTION:
    {
        luaX_next(ls);
        body(ls, v, 0, ls->linenumber);
        return;
    }
    default:
    {
        primaryexp(ls, v);
        return;
    }
    }

    luaX_next(ls);
}

static UnOpr getunopr (int op)
{
    switch (op)
    {
    case TK_NOT: return OPR_NOT;
    case '-': return OPR_MINUS;
    case '#': return OPR_LEN;
    }

    return OPR_NOUNOPR;
}

static BinOpr getbinopr (int op)
{
    switch (op)
    {
    case '+': return OPR_ADD;
    case '-': return OPR_SUB;
    case '*': return OPR_MUL;
    case '/': return OPR_DIV;
    case '%': return OPR_MOD;
    case '^': return OPR_POW;
    case TK_CONCAT: return OPR_CONCAT;
    case TK_NE: return OPR_NE;
    case TK_EQ: return OPR_EQ;
    case '<': return OPR_LT;
    case TK_LE: return OPR_LE;
    case '>': return OPR_GT;
    case TK_GE: return OPR_GE;
    case TK_AND: return OPR_AND;
    case TK_OR: return OPR_OR;
    }

    return OPR_NOBINOPR;
}

static const struct
{
  lu_byte left;  /* left priority for each binary operator */
  lu_byte right; /* right priority */
} priority[] = {  /* ORDER OPR */
   {6, 6}, {6, 6}, {7, 7}, {7, 7}, {7, 7},  /* `+' `-' `/' `%' */
   {10, 9}, {5, 4},                 /* power and concat (right associative) */
   {3, 3}, {3, 3},                  /* equality and inequality */
   {3, 3}, {3, 3}, {3, 3}, {3, 3},  /* order */
   {2, 2}, {1, 1}                   /* logical (and/or) */
};

#define UNARY_PRIORITY	8  /* priority for unary operators */


/*
** subexpr -> (simpleexp | unop subexpr) { binop subexpr }
** where `binop' is any binary operator with a priority higher than `limit'
*/
static BinOpr subexpr (LexState *ls, expdesc *v, unsigned int limit)
{
    callstack_ref cref( *ls->L );

    UnOpr uop = getunopr(ls->t.token);

    FuncState *fs = GetCurrentFuncState( ls );

    if (uop != OPR_NOUNOPR)
    {
        luaX_next(ls);
        subexpr(ls, v, UNARY_PRIORITY);
        luaK_prefix(fs, uop, v);
    }
    else
    {
        simpleexp(ls, v);
    }

    /* expand while operators have priorities higher than `limit' */
    BinOpr op = getbinopr(ls->t.token);

    while (op != OPR_NOBINOPR && priority[op].left > limit)
    {
        luaX_next(ls);
        luaK_infix(fs, op, v);
        /* read sub-expression with higher priority */
        expdesc v2;
        BinOpr nextop = subexpr(ls, &v2, priority[op].right);
        luaK_posfix(fs, op, v, &v2);
        op = nextop;
    }

    return op;  /* return first untreated operator */
}

static void expr (LexState *ls, expdesc *v)
{
    subexpr(ls, v, 0);
}

/* }==================================================================== */

/*
** {======================================================================
** Rules for Statements
** =======================================================================
*/

static int block_follow (int token)
{
    switch (token)
    {
    case TK_ELSE: case TK_ELSEIF: case TK_END:
    case TK_UNTIL: case TK_EOS:
        return 1;
    }

    return 0;
}

static void block (LexState *ls)
{
    /* block -> chunk */
    FuncState *fs = GetCurrentFuncState( ls );
    BlockCnt bl;
    enterblock(fs, &bl, 0);
    chunk(ls);
    lua_assert(bl.breaklist == NO_JUMP);
    leaveblock(fs);
}

/*
** structure to chain all variables in the left-hand side of an
** assignment
*/
struct LHS_assign
{
    struct LHS_assign *prev;
    expdesc v;  /* variable (global, local, upvalue, or indexed) */
};


/*
** check whether, in an assignment to a local variable, the local variable
** is needed in a previous assignment (to a table). If so, save original
** local value in a safe place and use this safe copy in the previous
** assignment.
*/
static void check_conflict (LexState *ls, struct LHS_assign *lh, expdesc *v)
{
    FuncState *fs = GetCurrentFuncState( ls );
    int extra = fs->freereg;  /* eventual position to save local variable */
    int conflict = 0;

    for (; lh; lh = lh->prev)
    {
        if (lh->v.k == VINDEXED)
        {
            if (lh->v.u.s.info == v->u.s.info)
            {  /* conflict? */
                conflict = 1;
                lh->v.u.s.info = extra;  /* previous assignment will use safe copy */
            }

            if (lh->v.u.s.aux == v->u.s.info)
            {  /* conflict? */
                conflict = 1;
                lh->v.u.s.aux = extra;  /* previous assignment will use safe copy */
            }
        }
    }
    if (conflict)
    {
        luaK_codeABC(fs, OP_MOVE, fs->freereg, v->u.s.info, 0);  /* make copy */
        luaK_reserveregs(fs, 1);
    }
}

static void assignment (LexState *ls, struct LHS_assign *lh, int nvars)
{
    FuncState *fs = GetCurrentFuncState( ls );
    expdesc e;

    check_condition(ls, VLOCAL <= lh->v.k && lh->v.k <= VINDEXED, "syntax error");

    if (testnext(ls, ','))
    {  /* assignment -> `,' primaryexp assignment */
        struct LHS_assign nv;
        nv.prev = lh;

        primaryexp(ls, &nv.v);

        if (nv.v.k == VLOCAL)
        {
            check_conflict(ls, lh, &nv.v);
        }

        luaY_checklimit(fs, nvars, LUAI_MAXCCALLS - ls->L->nCcalls, "variables in assignment");

        assignment(ls, &nv, nvars+1);
    }
    else
    {  /* assignment -> `=' explist1 */
        int nexps;
        checknext(ls, '=');
        nexps = explist1(ls, &e);

        if (nexps != nvars)
        {
            adjust_assign(ls, nvars, nexps, &e);

            if (nexps > nvars)
            {
                fs->freereg -= nexps - nvars;  /* remove extra values */
            }
        }
        else
        {
            luaK_setoneret(fs, &e);  /* close last expression */
            luaK_storevar(fs, &lh->v, &e);
            return;  /* avoid default */
        }
    }

    init_exp(&e, VNONRELOC, fs->freereg-1);  /* default assignment */

    luaK_storevar(fs, &lh->v, &e);
}

static int cond (LexState *ls)
{
    /* cond -> exp */
    expdesc v;
    expr(ls, &v);  /* read condition */

    if (v.k == VNIL)
    {
        v.k = VFALSE;  /* `falses' are all equal here */
    }

    FuncState *fs = GetCurrentFuncState( ls );

    luaK_goiftrue(fs, &v);
    return v.f;
}

static void breakstat (LexState *ls)
{
    FuncState *fs = GetCurrentFuncState( ls );
    BlockCnt *bl = (BlockCnt*)fs->blockList.GetFirst();
    int upval = 0;

    while (bl && !bl->isbreakable)
    {
        upval |= bl->upval;
        bl = (BlockCnt*)bl->next;
    }

    if (!bl)
    {
        luaX_syntaxerror(ls, "no loop to break");
    }

    if (upval)
    {
        luaK_codeABC(fs, OP_CLOSE, bl->nactvar, 0, 0);
    }

    luaK_concat(fs, &bl->breaklist, luaK_jump(fs));
}

static void whilestat (LexState *ls, int line)
{
    /* whilestat -> WHILE cond DO block END */
    FuncState *fs = GetCurrentFuncState( ls );
    int whileinit;
    int condexit;
    BlockCnt bl;
    luaX_next(ls);  /* skip WHILE */
    whileinit = luaK_getlabel(fs);
    condexit = cond(ls);
    enterblock(fs, &bl, 1);
    checknext(ls, TK_DO);
    block(ls);
    luaK_patchlist(fs, luaK_jump(fs), whileinit);
    check_match(ls, TK_END, TK_WHILE, line);
    leaveblock(fs);
    luaK_patchtohere(fs, condexit);  /* false conditions finish the loop */
}

static void repeatstat (LexState *ls, int line)
{
    /* repeatstat -> REPEAT block UNTIL cond */
    FuncState *fs = GetCurrentFuncState( ls );
    int repeat_init = luaK_getlabel(fs);
    BlockCnt bl1, bl2;

    enterblock(fs, &bl1, 1);  /* loop block */
    enterblock(fs, &bl2, 0);  /* scope block */

    luaX_next(ls);  /* skip REPEAT */

    chunk(ls);
    check_match(ls, TK_UNTIL, TK_REPEAT, line);
    int condexit = cond(ls);  /* read condition (inside scope block) */

    if (!bl2.upval)
    {  /* no upvalues? */
        leaveblock(fs);  /* finish scope */
        luaK_patchlist(fs, condexit, repeat_init);  /* close the loop */
    }
    else
    {  /* complete semantics when there are upvalues */
        breakstat(ls);  /* if condition then break */
        luaK_patchtohere(fs, condexit);  /* else... */
        leaveblock(fs);  /* finish scope... */
        luaK_patchlist(fs, luaK_jump(fs), repeat_init);  /* and repeat */
    }

    leaveblock(fs);  /* finish loop */
}

static int exp1 (LexState *ls)
{
    expdesc e;
    expr(ls, &e);

    int k = e.k;

    FuncState *fs = GetCurrentFuncState( ls );

    luaK_exp2nextreg(fs, &e);
    return k;
}

static void forbody (LexState *ls, int base, int line, int nvars, int isnum)
{
    /* forbody -> DO block */
    BlockCnt bl;
    FuncState *fs = GetCurrentFuncState( ls );

    adjustlocalvars(ls, 3);  /* control variables */

    checknext(ls, TK_DO);

    int prep = isnum ? luaK_codeAsBx(fs, OP_FORPREP, base, NO_JUMP) : luaK_jump(fs);

    enterblock(fs, &bl, 0);  /* scope for declared variables */

    adjustlocalvars(ls, nvars);
    luaK_reserveregs(fs, nvars);
    block(ls);

    leaveblock(fs);  /* end of scope for declared variables */

    luaK_patchtohere(fs, prep);

    int endfor = (isnum) ?
        luaK_codeAsBx(fs, OP_FORLOOP, base, NO_JUMP) : luaK_codeABC(fs, OP_TFORLOOP, base, 0, nvars);

    luaK_fixline(fs, line);  /* pretend that `OP_FOR' starts the loop */

    luaK_patchlist(fs, (isnum ? endfor : luaK_jump(fs)), prep + 1);
}


static void fornum (LexState *ls, TString *varname, int line)
{
    /* fornum -> NAME = exp1,exp1[,exp1] forbody */
    FuncState *fs = GetCurrentFuncState( ls );
    int base = fs->freereg;

    new_localvarliteral(ls, "(for index)", 0);
    new_localvarliteral(ls, "(for limit)", 1);
    new_localvarliteral(ls, "(for step)", 2);
    new_localvar(ls, varname, 3);

    checknext(ls, '=');
    exp1(ls);  /* initial value */

    checknext(ls, ',');
    exp1(ls);  /* limit */

    if (testnext(ls, ','))
    {
        exp1(ls);  /* optional step */
    }
    else
    {  /* default step = 1 */
        luaK_codeABx(fs, OP_LOADK, fs->freereg, luaK_numberK(fs, 1));
        luaK_reserveregs(fs, 1);
    }

    forbody(ls, base, line, 1, 1);
}

static void forlist (LexState *ls, TString *indexname)
{
    /* forlist -> NAME {,NAME} IN explist1 forbody */
    FuncState *fs = GetCurrentFuncState( ls );
    expdesc e;
    int nvars = 0;
    int base = fs->freereg;

    /* create control variables */
    new_localvarliteral(ls, "(for generator)", nvars++);
    new_localvarliteral(ls, "(for state)", nvars++);
    new_localvarliteral(ls, "(for control)", nvars++);

    /* create declared variables */
    new_localvar(ls, indexname, nvars++);

    while (testnext(ls, ','))
    {
        new_localvar(ls, str_checkname(ls), nvars++);
    }

    checknext(ls, TK_IN);

    int line = ls->linenumber;
    adjust_assign(ls, 3, explist1(ls, &e), &e);

    luaK_checkstack(fs, 3);  /* extra space to call generator */

    forbody(ls, base, line, nvars - 3, 0);
}

static void forstat (LexState *ls, int line)
{
    /* forstat -> FOR (fornum | forlist) END */
    FuncState *fs = GetCurrentFuncState( ls );
    TString *varname;
    BlockCnt bl;

    enterblock(fs, &bl, 1);  /* scope for loop and control variables */

    luaX_next(ls);  /* skip `for' */

    varname = str_checkname(ls);  /* first variable name */

    switch (ls->t.token)
    {
    case '=':
        fornum(ls, varname, line);
        break;
    case ',': case TK_IN:
        forlist(ls, varname);
        break;
    default:
        luaX_syntaxerror(ls, LUA_QL("=") " or " LUA_QL("in") " expected");
        break;
    }

    check_match(ls, TK_END, TK_FOR, line);

    leaveblock(fs);  /* loop scope (`break' jumps to this point) */
}

static int test_then_block (LexState *ls)
{
    /* test_then_block -> [IF | ELSEIF] cond THEN block */
    int condexit;
    luaX_next(ls);  /* skip IF or ELSEIF */
    condexit = cond(ls);
    checknext(ls, TK_THEN);
    block(ls);  /* `then' part */
    return condexit;
}

static void ifstat (LexState *ls, int line)
{
    /* ifstat -> IF cond THEN block {ELSEIF cond THEN block} [ELSE block] END */
    FuncState *fs = GetCurrentFuncState( ls );
    int escapelist = NO_JUMP;

    int flist = test_then_block(ls);  /* IF cond THEN block */

    while (ls->t.token == TK_ELSEIF)
    {
        luaK_concat(fs, &escapelist, luaK_jump(fs));
        luaK_patchtohere(fs, flist);
        flist = test_then_block(ls);  /* ELSEIF cond THEN block */
    }

    if (ls->t.token == TK_ELSE)
    {
        luaK_concat(fs, &escapelist, luaK_jump(fs));
        luaK_patchtohere(fs, flist);
        luaX_next(ls);  /* skip ELSE (after patch, for correct line info) */
        block(ls);  /* `else' part */
    }
    else
    {
        luaK_concat(fs, &escapelist, flist);
    }

    luaK_patchtohere(fs, escapelist);

    check_match(ls, TK_END, TK_IF, line);
}

static void localfunc (LexState *ls)
{
    expdesc v, b;
    FuncState *fs = GetCurrentFuncState( ls );

    new_localvar(ls, str_checkname(ls), 0);

    init_exp(&v, VLOCAL, fs->freereg);

    luaK_reserveregs(fs, 1);
    adjustlocalvars(ls, 1);

    body(ls, &b, 0, ls->linenumber);

    luaK_storevar(fs, &v, &b);

    /* debug information will only see the variable after this point! */
    getlocvar(fs, fs->nactvar - 1).startpc = fs->pc;
}

static void localstat (LexState *ls)
{
    /* stat -> LOCAL NAME {`,' NAME} [`=' explist1] */
    int nvars = 0;
    int nexps;
    expdesc e;

    do
    {
        new_localvar(ls, str_checkname(ls), nvars++);
    }
    while (testnext(ls, ','));

    if (testnext(ls, '='))
    {
        nexps = explist1(ls, &e);
    }
    else
    {
        e.k = VVOID;
        nexps = 0;
    }

    adjust_assign(ls, nvars, nexps, &e);

    adjustlocalvars(ls, nvars);
}

static int funcname (LexState *ls, expdesc *v)
{
    /* funcname -> NAME {field} [`:' NAME] */
    int needself = 0;
    singlevar(ls, v);

    while (ls->t.token == '.')
    {
        field(ls, v);
    }

    if (ls->t.token == ':')
    {
        needself = 1;
        field(ls, v);
    }

    return needself;
}

static void funcstat (LexState *ls, int line)
{
    /* funcstat -> FUNCTION funcname body */
    expdesc v, b;

    luaX_next(ls);  /* skip FUNCTION */

    int needself = funcname(ls, &v);

    body(ls, &b, needself, line);

    FuncState *fs = GetCurrentFuncState( ls );

    luaK_storevar(fs, &v, &b);

    luaK_fixline(fs, line);  /* definition `happens' in the first line */
}

static void exprstat (LexState *ls)
{
    /* stat -> func | assignment */
    FuncState *fs = GetCurrentFuncState( ls );

    struct LHS_assign v;
    primaryexp(ls, &v.v);

    if (v.v.k == VCALL)  /* stat -> func */
    {
        SETARG_C(getcode(fs, &v.v), 1);  /* call statement uses no results */
    }
    else
    {  /* stat -> assignment */
        v.prev = NULL;
        assignment(ls, &v, 1);
    }
}

static void retstat (LexState *ls)
{
    /* stat -> RETURN explist */
    FuncState *fs = GetCurrentFuncState( ls );
    expdesc e;
    int first, nret;  /* registers with returned values */

    luaX_next(ls);  /* skip RETURN */

    if (block_follow(ls->t.token) || ls->t.token == ';')
    {
        first = nret = 0;  /* return no values */
    }
    else
    {
        nret = explist1(ls, &e);  /* optional return values */

        if (hasmultret(e.k))
        {
            luaK_setmultret(fs, &e);

            if (e.k == VCALL && nret == 1)
            {  /* tail call? */
                SET_OPCODE(getcode(fs,&e), OP_TAILCALL);

                lua_assert(GETARG_A(getcode(fs,&e)) == fs->nactvar);
            }

            first = fs->nactvar;

            nret = LUA_MULTRET;  /* return all values */
        }
        else
        {
            if (nret == 1)  /* only one single value? */
            {
                first = luaK_exp2anyreg(fs, &e);
            }
            else
            {
                luaK_exp2nextreg(fs, &e);  /* values must go to the `stack' */
                first = fs->nactvar;  /* return all `active' values */

                lua_assert(nret == fs->freereg - first);
            }
        }
    }

    luaK_ret(fs, first, nret);
}

static int statement (LexState *ls)
{
    int line = ls->linenumber;  /* may be needed for error messages */

    switch (ls->t.token)
    {
    case TK_IF:
    {  /* stat -> ifstat */
        ifstat(ls, line);
        return 0;
    }
    case TK_WHILE:
    {  /* stat -> whilestat */
        whilestat(ls, line);
        return 0;
    }
    case TK_DO:
    {  /* stat -> DO block END */
        luaX_next(ls);  /* skip DO */
        block(ls);
        check_match(ls, TK_END, TK_DO, line);
        return 0;
    }
    case TK_FOR:
    {  /* stat -> forstat */
        forstat(ls, line);
        return 0;
    }
    case TK_REPEAT:
    {  /* stat -> repeatstat */
        repeatstat(ls, line);
        return 0;
    }
    case TK_FUNCTION:
    {
        funcstat(ls, line);  /* stat -> funcstat */
        return 0;
    }
    case TK_LOCAL:
    {  /* stat -> localstat */
        luaX_next(ls);  /* skip LOCAL */

        if (testnext(ls, TK_FUNCTION))  /* local function? */
        {
            localfunc(ls);
        }
        else
        {
            localstat(ls);
        }

        return 0;
    }
    case TK_RETURN:
    {  /* stat -> retstat */
        retstat(ls);
        return 1;  /* must be last statement */
    }
    case TK_BREAK:
    {  /* stat -> breakstat */
        luaX_next(ls);  /* skip BREAK */
        breakstat(ls);
        return 1;  /* must be last statement */
    }
    default:
    {
        exprstat(ls);
        return 0;  /* to avoid warnings */
    }
    }
}

static void chunk (LexState *ls)
{
    /* chunk -> { stat [`;'] } */
    int islast = 0;
    callstack_ref cref( *ls->L );

    while (!islast && !block_follow(ls->t.token))
    {
        islast = statement(ls);
        testnext(ls, ';');

        FuncState *fs = GetCurrentFuncState( ls );

        lua_assert(fs->f->maxstacksize >= fs->freereg && fs->freereg >= fs->nactvar);

        fs->freereg = fs->nactvar;  /* free registers */
    }
}

/* }====================================================================== */
